Although much of the public has
never heard of endocrine disruptors, the federal government has
been aware of their potential hazards in water for the past several
years. Congress included specific language on endocrine disruption
in the Food Quality Protection Act and amended Safe Drinking Water
Act in 1996. The former mandated that U.S. Environmental Protection
Agency (USEPA) develop an endocrine disruptor screening program,
whereas the latter authorizes USEPA to screen endocrine disruptors
found in drinking water sources.

While the USEPA does
have extensive data on pesticides-including some endocrine-related
data-there currently isn't enough scientific data available on most
of the estimated 87,000 chemicals currently in commerce to allow
assessment of all potential risks. The Endocrine Disruptor Screening
Program will enable USEPA to gather the information necessary to
identify endocrine disruptors and take appropriate regulatory action.

Endocrine disruptors defined
Development of animals and humans is, in part, controlled by a system
of hormones that signal growth, sexual development and many other
essential functions. This hormone system, also known as the endocrine
system, includes such organs as the testicles, ovaries and the thyroid,
pituitary and adrenal glands. The function of the system is to regulate
a wide range of biological processes, including control of blood
sugar, growth and function of reproductive systems, regulation of
metabolism, brain and nervous system development, and development
of an organism from conception through adulthood and old age.

Hormones such as estrogen
and testosterone are produced by the body to set off specific chemical
reactions in cells and initiate the performance of specific actions.
Unfortunately, a number of artificially produced chemicals can mimic
natural hormones and block cell receptor sites or trigger actions,
altering the body's natural growth and development. These interfering
chemicals are known as endocrine disruptors and scientists have
identified more than 60 in our environment, including water. Endocrine
disruption is one of the highest priority research topics for the
USEPA.

Biological impact
Evaluation of health impacts of endocrine disruptors in humans has
been more difficult to document, since exposure has little effect
on the exposed organism but rather may have drastic effects on the
offspring of that organism. Health effects on humans include lower
sperm counts, undescended testicles, early puberty and thyroid dysfunction.

Animals from alligators
to hamsters have been adversely effected by endocrine disruptors,
both in the laboratory and in the environment. Some effects on wildlife
include reproductive abnormalities, thyroid dysfunction, and feminization
of males or masculinization of females. Following exposure to endocrine
disruptors, birds have been born with crossed beaks, alligators
have been born with abnormally small penises, frogs born with multiple
legs and an overabundance of either male or female populations of
fish have been noted. Wildlife researchers have shown an adverse
relationship between endocrine disruptors and mating and parenting
behavior, immune response, sexual development, or breeding abilities
in a variety of species, such as terns, gulls, harbor seals, bald
eagles, beluga whales, lake trout, panthers, turtles and others.

Most of the documented
health problems have been associated with relatively high concentrations
of pesticides. Whether similar effects are occurring in the general
human or wildlife populations from exposures to ambient environmental
concentrations is unknown. What's known is there have been reports
of declines in the quantity and quality of sperm production in humans
over the last four decades, although other studies show no decrease.
Scientist fear reported increases in incidences of certain cancers
(breast, testes, prostate) may be related to endocrine disruption
and that even small disturbances in endocrine function may have
profound and lasting effects. Perhaps, most importantly, there are
concerns over the potential for synergistic effects from exposure
to multiple contaminants. Undoubtedly, the seriousness of the endocrine
disruptor hypothesis and the many scientific uncertainties associated
with the issue are sufficient to warrant a coordinated federal research
effort.

Chemical sources
Many chemicals have already been identified as endocrine disrupting,
including dioxins, polychlorinated biphenyls (PCBs) and DDT (see
Table 1). Although PCBs and DDT have been banned in this
country since the 1970s, they're still used in other parts of the
world. Other sources of endocrine disrupting chemicals include common
household items such as detergents, cosmetics, household cleaners
and plastic food containers with nonyl phenol, alkylphenol ethoxylates
and phthalates. Although pesticides play a vital role in controlling
agricultural and public health nuisances, most endocrine disruptors
in the environment are from pesticide applications. For this reason,
risks and benefits of specific pesticide use must be evaluated.

We typically ingest
endocrine disruptors via food and water. Some endocrine disrupting
chemicals are slow to degrade and persist in the environment, where
they may accumulate in the fatty tissue of organisms and increase
in concentration as they move up through the food chain, known as
bioaccumulation.

Control measures
The issue of endocrine disruptors and their impact on biological
organisms isn't being taken lightly by governmental or industrial
groups. For instance, the Laboratory of Reproductive and Development
Toxicology, at the National Institute of Environmental Health Sciences
(NIEHS), is analyzing structures through molecular modeling, searching
for the chemical keys that open a receptor's lock and trigger hormonal
activities. The group hopes to eventually develop a predictive screening
device identifying endocrine disrupting chemicals and are particularly
interested in the dose-response relationship, since low levels appear
to contribute to human disease. Of its $280 million budget, NIEHS
spends about $30 million a year on endocrine-related research.

Industries that produce
suspected endocrine disruptors have also initiated new research
programs. In particular, the chemical industry is funding a $1.5
million-a-year endocrine disruptor research program at the Chemical
Industry Institute of Toxicology. That program plans research on
receptor-mediated mechanisms; assessment of endocrine modulation
in animals; metabolism, disposition, pharmacokinetics and homeostasis
of such chemicals; and biomathematical modeling of reproductive
endocrine systems.

Also the Endocrine
Issues Coalition, formed early this year and meets every few months
to share industry research. It's made up of the Chemical Manufacturers
Association (CMA), Chlorine Chemistry Council, National Crop Protection
Association, Society of the Plastics Industry, American Forest and
Paper Association and American Petroleum Institute.

Endocrine disruptors
were recognized as an initiative in November 1995, by the NSTC (National
Science and Technology Council) Committee on Environment and Natural
Resources (CENR), a cabinet-level council chaired by President Clinton
that serves as the principal means for coordinating science and
technology issues across the federal government. The CENR established
a Working Group on endocrine disruptors that's chaired by the USEPA
with vice chairs from the Department of the Interior and the NIEHS.

Other participating
agencies include the National Oceanic and Atmospheric Administration,
National Science Foundation, Food and Drug Administration, Centers
for Disease Control, Agency for Toxic Substances and Disease Registry,
National Cancer Institute, Smithsonian Institution, the Departments
of Agriculture and Energy, and the Office of Science and Technology
Policy. This concerted effort is aimed at gathering more information
on the potential health risks of endocrine disruptors and the need
for possible regulation.

Conclusion
While there's no direct evidence from human studies to confirm a
causal link between exposure and effect, concern exists and is strengthened
by reports of adverse reproductive and developmental effects in
wildlife, possibly mediated via endocrine disruptive pathways. Water
treatment processes designed to remove carcinogens and pesticides
are effective at removal of those agents identified as endocrine
disruptors. More difficult to control is the recreational waterborne
route and the bioaccumulation of endocrine disruptors in aquatic
species.

As research continues
and public awareness increases, the next decade promises to reveal
the true impact and breadth of endocrine disrupting chemicals.

About
the authorDr. Kelly
A. Reynolds is a research scientist at the University of Arizona with
a focus on the development of rapid methods for detecting human pathogenic
viruses in drinking water. She is also a member of the WC&P Technical
Review Committee.